Field of the Invention
The present invention relates to a method for manufacturing a hollow molded article by performing vacuum molding of two thermoplastic resin sheets and an apparatus for molding a hollow molded article.
Description of the Related Art
Japanese Patent Application, Publication No. 2010-83144 discloses a method for manufacturing a hollow body made up of at least two thermoplastic resin sheets, using a metal mold having a pair of metal mold members freely movable in a predetermined direction. The metal mold members have a molding surface capable of suctioning air, and an outer circumferential section (a flange) that surrounds the molding surface. Further, the use of a foamed sheet as the thermoplastic resin sheet is disclosed.
The above-described conventional manufacturing method has a supplying process of supplying the laminated thermoplastic resin sheets between the metal mold members, a heating process of heating the thermoplastic resin sheets; a mold clamping process of relatively bringing the metal mold members closer to each other and integrally pressing the respective heated thermoplastic resin sheets between the outer edge sections of the metal mold members to integrate each sheet in a section pressed at the outer edge sections; and a shaping process of feeding air into a space formed between the thermoplastic resin sheets, while suctioning air out from the molding surface, causing the respective thermoplastic resin sheets facing the mold surface to follow the molding surface, and shaping the thermoplastic resin sheets into a predetermined shape.
In the above-described shaping process, a method for interposing a tube 2 between a sheet 1 and a sheet 1 and introducing the external air through the tube is described as a method for feeding air into the space formed between the thermoplastic resin sheets, in paragraph 0021, with reference to FIG. 3, at the time of the above-described supplying process. Further, the same paragraph discloses that the temperature of the air fed from the tube 32 is preferably 60 to 200□ C. in order to improve moldability, and a compressor or the like is connected to one end of the tube 32 to feed the air. Further, paragraph 0022 discloses a decompressing process of reducing the pressure of a space 31 formed between the sheets 1 by connecting a pump to one end of the tube. Further, paragraph number 0023 discloses that a process of feeding the air into the space 31 again after the completion of the decompressing process may be further included.
However, in the above-described conventional manufacturing method, in the supplying process, a tube for feeding air into the space formed between the sheets is required to be interposed between the sheet and the sheet. Therefore, there is a need for a device for inserting and holding the tube, however, a generally used vacuum molding machine does not have a device for operating the tube. Therefore, a dedicated device for operating the tube is required to perform the above-described conventional manufacturing method.
An object of an aspect of the present invention is to provide a method for manufacturing a hollow molded article that is capable of stably manufacturing the hollow molded article, without causing a hollow structure evacuation, and is capable of manufacturing the hollow molded article, using a general-purpose vacuum molding machine, without separately requiring a facility and device for feeding air between the two sheets.
Another object of an aspect of the present invention is to provide a method for manufacturing a hollow molded article that is capable of manufacturing the hollow molded article with a simple structure, by configuring so that air is naturally suctioned into between the two thermoplastic resin sheets, accompanying the progress of vacuum molding of the thermoplastic resin sheet.